Light bulbs usually provide light that includes all the colors in the rainbow: violet, blue, green, yellow, orange, and red. When all of these colors are present, the light is known as “white light.” The rainbow, which is the separated colors, is known as a spectrum. Different kinds of light bulbs provide different quantities of the various colors, which means, for example, that some light bulbs provide more red light than blue light, while other light bulbs provide more green light than orange light. In addition, most light bulbs also provide light that is not visible to the naked eye, such as ultraviolet (UV) light and infrared (IR) light.
The different colors of light are known as different wavelengths of light, and range in the visible spectrum from violet or blue light having a wavelength of about 400 nm to red light having a wavelength of about 700 nm; UV light is typically between about 300 nm to 400 nm, and IR light is typically from about 700 nm to 1000 nm.
For a long time, people have wanted to select specific wavelengths and/or intensities of light for specific situations, such as for lighting a movie scene so that it looks like the middle of a bright summer day in Mexico City or a cool fall evening with a beautiful sunset in Anchorage, Ak., for diagnosing or treating disease, for measuring or analyzing the chemical or physical properties of an object, or for initiating a physical or chemical change in an object or compound or organism.
In order to obtain particular wavelengths and intensities of light, movie sets employ highly skilled and specialized lighting technicians that use very expensive light bulbs, lighting apparatus, lighting filters (such as colored “gels”), and the like. The intense heat generated by the lights, however, reaches oven-like temperatures and can cook film, filters, and lighting elements. Other situations likewise employ expensive personnel and apparatus.
In some previous attempts to deal with these problems, a spectrum former, such as a prism, has been placed in front of the light bulb to separate the light beam into its respective wavelengths, then a transmissive pixelated spatial light modulator has been placed in the spectrum. A pixelated spatial light modulator is typically a square or rectangular device (although other shapes are possible) that contains a large number of tiny pixels and can be turned on or off at will. Turning a line of pixels “on” while turning all others “off” permits the spatial light modulator to pick a specific color of light; more complex on/off patterns can pick more complex wavelength and intensity distributions. However, these prior attempts have been problematic because the pixelated spatial light modulators have either absorbed the undesired light or reflected it back to the original light source or spectrum former. In either case, the heat from the undesired light is not dissipated and serious problems may ensue.
Thus, there has gone unmet a need for lighting systems and luminaires that provide selected light wavelengths and intensities but that do not overheat, and that can also rapidly switch between different selected wavelengths or intensities, including highly complex groupings of wavelengths or intensities. The present invention provides these and other advantages.